Scrum doesn’t state anything about deadlines being communicated. The fact is, business objectives have to be met, and they often come with constraints.
The retro is seems like the first meeting to get cut from the normal sprint cadence. But don't give it up! Everybody benefits, whether they know it or not.
Vertical slicing fosters a better team spirit and a better understanding of how to tackle new tasks – leading to more happiness, confidence, and creativity.
Agile iteration meetings often fall prey to unproductive activities and lack of focus. Scrum practices can make meetings more structured and effective.